(display "\n========================================\n")
(define (double f)
    (lambda (x) (f (f x))))

(define (inc x)
    (+ x 1))

(display (inc 5))
(newline)
(display ((double inc) 5))
(newline)
(display ((double (double inc)) 5))
(newline)
(display (((double (double double)) inc) 5))
(display "\n========================================\n")
